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MOD Exam 3 > Protozoa Infections > Flashcards

Protozoa Infections Flashcards

(15 cards)

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1
Q

Entamoeba histolytica:

  • Transmission?
  • Morphology?
  • Clinical Findings?
  • Diagnosis?
  • Miscellaneous?
A

• Transmission:
- Fecal-oral

• Morphology: 
AMOEBA 
1. Oocyst 
2. Trophozoite: motile 
- Bulls eye shaped nucleus, with red blood cells in the cytoplasm

• Clinical Findings:

  1. Asymptomatic carriage
  2. BLOODY diarrhea: when trophozoites invade the intestinal mucosa, causing erosions
  3. Liver abscess

• Diagnosis:

  1. Fecal exam: look for cysts and trophozoites with red blood cells in their cytoplasm
  2. Serology
  3. Abdominal CT scan: look for liver abscesses

• Miscellaneous:

  1. Not all species of Entamoeba are pathogenic
  2. 90% of people infected with Entamoeba histolytica are ASYMPTOMATIC
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2
Q

Giardia lamblia:

  • Transmission?
  • Morphology?
  • Clinical Findings?
  • Diagnosis?
A

• Transmission:
- Fecal-oral

• Morphology:

  1. Oocyst
  2. FLAGELLATED trophozoite

• Clinical Findings:
- Foul smelling, greasy diarrhea (with high fat content), and abdominal gassy distension

• Diagnosis:

  1. Fecal exam: look for cysts and trophozoites
  2. Commercial immunoassay kit: Test stool
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3
Q

Cyclospora cayetanesis:

  • Transmission?
  • Morphology?
  • Clinical Findings?
  • Diagnosis?
  • Miscellaneous?
A

• Transmission:
- Oocysts from stool contaminate fruits and vegetables

• Morphology:
- Oocysts

• Clinical Findings:

  1. Watery diarrhea
  2. Nausea and vomiting

• Diagnosis:
- Stool exam reveals oocysts that fluoresce under UV light and are acid-fast

• Miscellaneous:
- Associated with strawberries and raspberries

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4
Q

Cryptosporidium:

  • Transmission?
  • Morphology?
  • Clinical Findings?
  • Diagnosis?
  • Miscellaneous?
A

• Transmission:
- Fecal-oral

• Morphology:

  1. Oocysts is infective agent (contains 4 sporozoites)
  2. Life cycle occurs within infected epithelial cells

• Clinical Findings:
- Watery diarrhea, vomiting and abdominal pain (usually self-limiting, but can be life-threatening in immunocompromised patients)

• Diagnosis:

  1. Fecal exam: look for oocyst
  2. Biopsy of lining of the small intestine

• Miscellaneous:
- Obligate intracellular parasite

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5
Q

Isospora species:

  • Transmission?
  • Morphology?
  • Clinical Findings?
  • Diagnosis?
  • Miscellaneous?
A

• Transmission:
- Fecal-oral

• Morphology:
- Oocyst is infective agent (contains 8 sporozoites)

• Clinical Findings:
- Severe diarrhea and malabsorption in AIDS patients

• Diagnosis:

  1. Fecal exam: look for oocyst (acid-fast or fluorescent stain required)
  2. Biopsy
  3. EOSINOPHILIA

• Miscellaneous:
- Obligate intracellular parasite

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6
Q

Trichomonas vaginalis:

  • Transmission?
  • Morphology?
  • Clinical Findings?
  • Diagnosis?
  • Miscellaneous?
A

• Transmission:
- Sexually transmitted

• Morphology:

  1. No cyst stage
  2. FLAGELLATED trophozoite

• Clinical Findings:

  1. Painful vaginal itching
  2. Burning on urination
  3. Yellow-green malodorous, frothy vaginal discharge

• Diagnosis:

  1. Examine vaginal discharge: identify these highly motile protozoa
  2. Examination of urine for these protozoa

• Miscellaneous:
- Provide metronidazole to the patient’s sexual partners

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7
Q

Naegleria fowleri:

  • Transmission?
  • Morphology?
  • Clinical Findings?
  • Diagnosis?
A

• Transmission:
- Lives in freshwater lakes

• Morphology:
- Amoeba

• Clinical Findings:
- Acute meningitis, which is usually fatal within a week

• Diagnosis:
- CSF exam: look for motile amoeba, as well as white blood cells (suggesting an infection)

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8
Q

Acanthamoeba species:

  • Transmission?
  • Morphology?
  • Clinical Findings?
  • Diagnosis?
  • Miscellaneous?
A

• Transmission:

  1. Lives in fresh water lakes
  2. Eye infections from dirty contact lenses

• Morphology:

  1. Amoeba stage
  2. Cyst stage in brain

• Clinical Findings:

  1. Chronic, granulomatous brain infection, which is fatal in a year
  2. Corneal infection: often associated with the use of contact lenses that are cleaned in non-sterile solutions

• Diagnosis:

  1. Examination of CSF and brain tissue: reveals both cysts and mature trophozoites
  2. Examination of corneal scrapings

• Miscellaneous:
- Corneal infection:
A. Topical antimicrobial agents
B. Corneal transplant

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9
Q

Toxoplasma gondii:

  • Transmission?
  • Morphology?
  • Clinical Findings?
  • Diagnosis?
  • Miscellaneous?
A

• Transmission:

  1. Ingestion of oocysts in raw pork
  2. Inhalation of oocysts from cat feces
  3. Congenital: if a pregnant women is exposed to Toxoplasma for the very first time, she can pass this infection to her fetus

• Morphology:

  1. Oocyst is infectious
  2. Trophozoites

• Clinical Findings:
1. Congenitally acquired (TOrches organism):
A. Still birth; chorioretinitis; blindness; seizures; mental retardation; microcephaly
B. Normal appearing infants may develop reactivation as adolescents or adults: chorioretinitis (which can lead to blindness)

  1. Immunocompromised patients: disseminated infection which may include:
    A. Encephalitis presenting as a brain mass
    B. Chorioretinitis
    C. Lymph node, liver, and spleen enlargement
    D. Pneumonia

• Diagnosis:

  1. Serology (high IgM and IgG titers)
  2. Radiology: CT scan shows contrast-enhancing mass in the brain
  3. Examination of the retina

• Miscellaneous:
- Obligate intracellular parasite

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10
Q

Pneumocystis carinii:

  • Transmission?
  • Morphology?
  • Clinical Findings?
  • Diagnosis?
  • Miscellaneous?
A

• Transmission:

  1. Acquired at an early age by respiratory route
  2. Remains latent in normal hosts

• Morphology:
- Flying-saucer appearing FUNGUS that was previously classified as a protozoan

• Clinical Findings:
- INTERSTITIAL PNEUMONIA: with fever and a dry, nonproductive cough. Major pathogen in AIDS patients (when CD4 count is less than 200)
A. 15% chance of infection/year in AIDS patients
B. 80% lifetime risk without prophylactic trimethoprim/sulfa

• Diagnosis:
1. Silver stain: to see flying saucer appearing fungi in:
A. Saline induced sputum
B. Bronchoalveolar lavage with bronchoscope

  1. X-ray: find an interstitial pneumonia, with diffuse infiltrates

• Miscellaneous:

  1. AIDS patients with CD4 positive T-cell counts less than 200 are susceptible
  2. The most common opportunistic infection in AIDS
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11
Q

Malaria:

  1. Plasmodium falciparum
  2. Plasmodium vivax
  3. Plasmodium ovale
  4. Plasmodium malariae
  5. Plasmodium knowlesi
  • Transmission?
  • Morphology?
  • Clinical Findings?
  • Diagnosis?
  • Miscellaneous?
A

• Transmission:
- Female anopheles mosquito

• Morphology: 
1. See life cycle diagram (Fig 31-7) 
2. HYPNOZOITE stage: 
dormant form that hangs out in the liver 
   A. P. vivax 
   B. P. ovale

• Clinical Findings:
MALARIA
1. Periodic episodes of high fever and shaking chills, followed by period of profuse sweating (sweats occur when the red blood cells burst and release merozoites)
A. TERTIAN malaria: episodes occur every 48 hours (P. vivax and P. ovale)
B. QUARTAN malaria: episodes occur every 72 hours (P. malariae)
C. P. falciparum (most common and deadly): irregular episodes
2. Anemia
3. Hepatomegaly
4. Splenomegaly (and occasionally splenic rupture)
5. Brain, lung, and/or kidney damage with P. falciparum

• Diagnosis:
1. Examination of blood smear reveals:
A. Trophozoites (diamond ring shaped)
B. Schizonts
C. Gametocytes
2. Rapid antigen diagnostics are available

• Miscellaneous:

  • Many African Americans are resistant to certain species of malaria:
    1. Red blood cells that lack the cell membrane antigens Duffy a and b provides resistance to infection by P. vivax
  1. SICKLE CELL ANEMIA TRAIT provides resistance to infection by P. falciparum
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12
Q

Babesia microti:

  • Transmission?
  • Morphology?
  • Clinical Findings?
  • Diagnosis?
  • Miscellaneous?
A

• Transmission:
- Ixodes scapularis tick

• Morphology:

  1. Sporozoites from tick cause infection
  2. Mature into trophozoites in humans and infect red blood cells.

• Clinical Findings:

  1. Immunocompetent: usually asymptomatic
  2. Immunocompromised: anemia due to hemolysis, fatigue, and protracted course

• Diagnosis:

  1. Blood smear
  2. PCR (more sensitive than blood smear)
  3. Serology

• Miscellaneous:

  1. Classic “maltese cross” on blood smear
  2. Patients may be co-infected with Lyme disease
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13
Q

Leishmania:

  1. Leishmania tropica
  2. Leishmania chagasi
  3. Leishmania major
  4. Leishmania braziliensis
  5. Leishmania donovani
  • Transmission?
  • Morphology?
  • Clinical Findings?
  • Diagnosis?
  • Miscellaneous?
A

• Transmission:

  1. SANDFLY bite
  2. Contaminated blood transfusion
  3. Zoonotic: carried by rodents, dogs, and foxes

• Morphology:

  • Promastigote: FLAGELLATED (in sandfly)
  • Amastigote: intracellular and non-flagellated: in phagocytic cells of the reticuloendothelial system (lymph nodes, spleen, liver and bone marrow)

• Clinical Findings:
1. CUTANEOUS leishmaniasis: single ulcer at site of the sandfly bite (oriental sore). Heals in a year, leaving a depigmented scar.

  1. DIFFUSE CUTANEOUS: nodules at bite site (which do not ulcerate) and over body (especially near the nose); can last 20 years without treatment
  2. MUCOCUTANEOUS: ulcers appear on mucous membranes after first ulcer at bite site heals. Ulcers erode the nasal septum, soft palate and lips. Can last 20-40 years.
  3. VISCERAL leishmaniasis (Kala-azar): common in young, malnourished children. Fever, anorexia, weight loss, and abdominal swelling (from hepatomegaly and massive splenomegaly). Often fatal

• Diagnosis:
1. Demonstation of protozoa
A. Blood smear
B. Biopsy of skin lesions, spleen or liver
2. Leishmanin skin test is negative in patients with low (defective) cell-mediated immunity
A. Diffuse cutaneous leishmaniasis
B. Active visceral leishmaniasis
3. Elevated serum anti-leishmanial IgG Ab titers

• Miscellaneous:
- The different diseases caused by Leishmania depend on the species, as well as the patient’s cell mediated immune response

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14
Q

African Trypanosome:

Trypanosoma rhodesiense
Trypanosoma gambiense

  • Transmission?
  • Morphology?
  • Clinical Findings?
  • Diagnosis?
  • Miscellaneous?
A

• Transmission:

  1. TSETSE FLY bite
  2. Contaminated blood transfusion

• Morphology:

  1. Trypomastigote is the motile (FLAGELLATED) extracellular form living in blood, lymph nodes, and CNS
  2. Trypomastigote and epimastigote: in tsetse fly

• Clinical Findings:
AFRICAN SLEEPING SICKNESS
1. Hard, red painful skin ulcer at the site of the tsetse fly bite, which heals in 2 weeks
2. Fever, headache, and lymph node swelling
3. Fevers subside, then relapses can occur (and last for months)
4. CNS symptoms develop: daytime drowsiness, behavioral changes, difficulty walking, slurred speech, coma and death
A. West African sleeping sickness (T. gambiense): slowly progressing fevers, wasting, and late neurologic symptoms
B. East African sleeping sickness (T. rhodesiense): more severe, with rapid cycling of fevers, leading to neurologic symptoms and death in weeks to months

• Diagnosis:

  1. Visualize trypomastigotes in blood, spinal fluid, or lymph nodes
  2. Serology (high IgM titers)
  3. Antibody agglutination test for T. gamiense

• Miscellaneous:
- ANTIGENIC VARIATION:
The trypanosomes express on their surface a new variable surface glycoprotein (VSG) in a cyclic nature. As antibodies form against a particular VSG, the trypanosome will produce progeny with a different VSG that can elude the immune response for a while. This is the mechanism for the recurrent fevers

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15
Q

American Trypanosome:
Trypanosome cruzi

  • Transmission?
  • Morphology?
  • Clinical Findings?
  • Diagnosis?
A

• Transmission:
1. KISSING BUG (reduviid bug): defecates on human skin while feeding. Trypomastigotes, present in the feces, tunnel into the skin

  1. Contaminated blood transfusion

• Morphology:
1. Trypomastigote is the motile (FLAGELLATED) extracellular form living in blood

  1. Amastigote: intracellular and nonmotile: present in macrophages, lymph nodes, and organs (heart and brain)
  2. Trypomastigote and epimastigote: in kissing bug

• Clinical Findings:
CHAGAS’ DISEASE:

  1. CHAGOMA: hardened red area at site of parasite entry
  2. ACUTE CHAGAS’ DISEASE: fever, malaise, and swollen lymph nodes
    A. Meningoencephalitis
    B. Acute myocarditis with tachycardia and EKG changes
  3. INTERMEDIATE phase: low levels of parasites in blood and positive antibodies against T. cruzi, but NO symptoms. Most persons remain in this phase for life
  4. CHRONIC Chagas’ disease (some people progress to this stage):
    A. Cardiomyopathy: dilated heart, heart failure, and arrhythmias
    B. MEGADISEASE: large dilated poorly functioning hollow organs lead to:
    1. Megacolon: constipation and abdominal pain
    2. Megaesophagus: difficulty and pain with swallowing, and vomiting of food

• Diagnosis:
Acute Chagas:
1. Visualize trypomastigotes in blood.
2. XENODIAGNOSIS: 40 laboratory grown reduviid bugs are allowed to feed on a patient. One month later the bugs’ intestinal contents re-examined for the parasite.

Chronic Chagas:
1. Clinical diagnosis supported by serology and/or PCR

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